Apparatus for control of highway crossing signals



Patented June 13, 1944 APPARATUS FOR CONTROL OF HIGHWAY CROSSING SIGNALS Easton E. Parrill, SwiSsvale, Pa.., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application August 1 8, 1942, Serial No. 455,171

' 4 Claims. .(01. 246130) My invention'relates' to apparatus for control of highway crossing signals, and more particularly to such apparatus using alternating current track circuits.

When alternating current track circuits are used-to control a highway crossing signal for a railway over which traific movesin either direc tion, no warning operation of the signal may result if a loss of the altematingcurrent occurs and power is restored while a train occupies an approach track section.

Accordingly, a feature of my invention is the provision of novel and improved apparatus for the control of highway crossing signals when alternating current track circuits are used.

Other features, objects and advantages of my invention will appear as the specification progresses.

I shall describe one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view showing one form of highway crossing signal control apparatus embodying my invention.

In the drawing the reference characters Ia and Ib designate the track rails of a stretch of railway over which traflic moves in either direction, and which stretch is intersected by a highway H, a highway crossing signal S being located at the intersection. The rails Ia and lb are formed by the usual insulated rail joints with two track sections IT and 2T which have their junction adjacent the intersection and extend in opposite directions therefrom, track section IT serving as an approach section for westbound traffic and section 2T serving as an approach section for eastbound traffic. Each track section IT and 2T is provided with an alternating current track circuit which includes'a track transformer connected across the rails at one end of the section and a track relay connected-across the rails at the other end of the section, the tracktransformer and relay being identified by the reference characters T and R, respectively, with a prefix corresponding to the section. These track transformers are supplied with alternating current from a suitable source, and as here'disclosed they are supplied with current from a enerator G connected to a transmission line comprising line wires LI and L2. Primary winding 5 of track transformer ITT is connected across the line wires LI and L2 and a'secondary winding 6 of this transformer is connected across the rails of section IT through a limiting resistor 1 to supply power to the track circuit of section IT. Similarly,'primary winding 8 or track transformer 2TT is connected acrossthe line wires, and a secondary winding 9 of this transformer is connected across the rails of sec tion 2T through a limiting resistor I0 to'supply power to the track circuit for section 2T. A power-off relay POR is provided and the winding of relay POR is connected to the line wires LI and L2 through a line transformer LT. Consequently relay POR is energizedand picked up'as long as alternating current is present in the transmission line, but is deenergized and released when an interruption of the supply of alternating current occurs.

The'track relays I'IR and ZTR, together with the power-01f relay POR govern a directional means to provide a directional control for signal S. As here shown, the directional means is an interlocking relay IR whose magnets'EXR. and

WXR. are associated with track sections IT and 2T, respectively. Interlocking relay IR is preferably of the direct current type having fiagman contacts, fiagman contactsIG and I9 being operated by the armatures of magnets EXR and WXR, respectively. Each fiagman contact I6 and I9 is closed when the respective magnet armature is picked up and remains closed when the respec-' tive armature is locked at the intermediate 'position of the relay, but is opened when the associated armature is the first one of the two tobe released. Each magnet EXR, and WXR is energized by two alternative circuits, one of which serves as a pick-up circuit, and the other one of which serves as a stick circuit. The energizing circuits for the magnets of the interlocking relays, as well as' the operating circuits for signal S, to'be referred to later, are supplied .with energy from an auxiliary source such as a battery AB. A first energizing or pick-up circuit for magnet EXR is formed from the top terminal of battery AB through front contact' II of "power-off relay POR, front contact I2 of track relay ITR, winding of magnet EXR. and wire I3 to the lower terminal of battery AB. A second energizing or stick circuit for magnet EXR can be traced from the top terminal of battery AB through back contact I4 of relay POR, back contact I5 of magnet WXR, fiagman contact I6 of magnet EXR, winding of magnet EXR, and wire I 3 to the lower terminal of battery-AB. Similarly, a first energizing circuit for the magnet WXR, includes top terminal of battery AB, front contact II of relay POR, front contact H of track relay 2TB, winding of magnet WXR, wire I3 and the lower terminal of battery AB; and a second energizing circuit for this magnet includes top terminal of battery AB, back contact M of relay POR, back contact l8 of magnet EXR, flagman contact IQ of magnet WXR, winding of magnet WXR, wire I3 and lower terminal of battery AB. Thus each magnet EXR and WXR is energized through its associated first energizing circuit when the alternating current is present and each track section is unoccupied, andeach magnet may be energized as will be pointed out presently through its second circuit when there is a loss of alternating current.

Each magnet EXR and WXR is preferably pro.-

vided with slow to release characteristics.

The highway crossing signal 3 may be of any desired form, such as, for example, a gate, a barrier, a flashing light, an audible signal or a combination of these devices, and it is shown as an audible signal in the form of an electric bell, The signal S is operated by energy from'auxiliary source AB, the operating circuit of signal S having three alternative paths, one of which includes back c tact '28 o m n t a seco d one of V which includes back contact 2| of ma net WXR, and a third one of which includes back contact 22 of power-off relay POR.

Nonnally, that is, when alternating current is present and the track sections IT and H are unpi cupied, the power-01f relay POR and the two track relays IT-R and 2TB are picked up causing the interlocking relay to be energized and signal S to be silent. If an eastbound train approaches the intersection-to shunt track relay 2TB. opening front contact ll, the magnet WXR of the interlocking relay is deenergized and its armature is released to its full down position where it closes the operating circuit for bell S at back contact 21 so that signal S is sounded to provide a warnin indication of the approach of this train. The interlocking mechanism of the relay IR. is actu ated by the release of the armature of magnet WXR so that when the train enters section IT toshunt track relay ITR and deenergize magnet EXR, the armature of 'magnet 'E'XR is locked at its intermediate position in the usual manner'for such .a relay. Consequently, when this train vacates the track section 2T and track relay 2TB ispicked up causing-magnet WXR to be reenerg-ized, the warning operation of signal S ceases andthe signal remains silent as this trainrecedes from the intersection through the track section IT. "If a westbound train approaches the intersection to shunt .track relay ITR opening front contact 12, magnet EXR is deenergized and its armature is released to the full downposltion closing the operating circuit of signal S at back contact :20 and signal S sounds its warning indi cation of the approach of this westbound train. The interlocking feature of the relay is actuated by the release of the armature of magnet EX R so that when magnet WXR is deenergized in re sponse to this westbound train entering section 2T, the armature of magnet WXR is locked at its intermediate position and signals is silent as the westbound train recedes from the inter: section through section IT. The above is the normal operation .of the apparatus as long as the alternating current is present. I

If a loss of alternating current on the transmis ion line occurs, the power-off relay and track relays areall .deenergized. The loss of power on the transmission line may be, and very often is, a gradual falling away of the voltage, with the 'fislilt that the relays POR, ITR and 2TH are not cleaners-iced simultaneously. If relay POR is reppwereofi relay,and also ahead of the other track the magnet of the interlocking relay associated with the first released track relay releases its man c first, and the armature of the other w nagnet is locked at its intermediate position.

That is to say, a loss of power may, and very frequently :does, :result in the interlocking relay being conditioned at a position corresponding to a directional selection. In any event, the loss of newer is e lowed by ope ation of si n l s, t operatine cirel it of sis-no] rs being completed at heckvcentcct 31 ct e ay con, and so at eithe back contact 20 or 2| of the interlocking. relay.

.ze sumins or illustration that there is' a loss of alt rnating current, a d ma net of relay 3 :isdccnctc scd ahead. of magnet so that t e armatur oi. magnet is locked at the intermediate position, the magnet WXR is :refine -sized cv rits second circuit including back contact ll of relay POR, back contact .18 of magnet; audits own :flagman contact 19. Conseguently vthearrnatureof magnet WXR is icked u on theimer ccking mechanism of the relay. If an eastbound atrain approaches the intersect on and while the train coupies axsection 2T, the 'altfimfltln current is restored, the restoration of power will reenergize relay POR and reapely power to. the track circuits. Track relay iSepersl-zed, but track relay 2TB. remains released due tc'the presence of the train in sectign gr. With relay FQR and track-relay ITR picked up, :the magnet EXR "is energized through ts first. circui and with both relay POR and o ml llfib m, energized, the operating circuit for i nals is open. ,Magnet WXR'which was energiced cveriits second or stick circuit now is deenergized because its first circuit is open at front contact H citrackrelay'lTR, and its stick circuit ,5 79pm at two points, back contact 14 of relay P98, and back contact 18 of magnet Because magnet WXRhadbeen previously energized and itsxarmature raised on the interlocking mechanisxn, its armature is now free to fall to the full down osition, closing the operating circuit for signal S at back contact 2| to warn highway users of the approach of this eastbound train, Interlocking relay -I-R being new conditioned to agree ith normal operation for an eastbound train, the-apparatus functions in the usual manner as this eastbound train passes over the intersection and recedes-through the track-section IT.

In the event a'westbound train approaches the intersection subsequent :to'the loss of power and theconditioning of the interlocking relay with ma net EXR released and magnet energizedzover its stick circuit, and power is restored while this westbound train occupies section 1T the power-off relay ROR and track relay are reenergized. Magnet WXR which had previously been energized through its stick circuit is now-energized throughits' first or pick-up circuit including front contact H of relay PQR and front contact I! of track relay Magnet which was the first to be released when a loss of power occurred, remains deenergized subsequent to the restoring of power due to the presence of the train in section IT, and consequently signals continues to be operated to provide its warning operation. Interlocking relay IR being now conditioned at the position corresponding to normal operation for a westbound train, the apparatus functions in the usual manner as this westbound'train recedes from the intersection through track section 2T.

It is to be pointed out that if the control of the interlocking relay by relay POR is not provided, and if the second circuit for magnet WXR is not provided and the interlocking relay is controlled alone by the track relays or by the track circuits direct, as has been the custom heretofore, and magnet EXR is the first to be deenergized subsequent to the loss of alternating current, the armature of magnet WXR would remain locked at the intermediate position subsequent to the loss of alternating current. If then power is restored while the eastbound train occupies section 2T, the armature of magnet WXR would have been held at the intermediate position and the signal S would have failed to provide its warning indication after relay PCB. and magnet EXR became deenergized due to the restoration of power. Further, with the armature of magnet WXR locked at its intermediate position, the armature of magnet EXR would be free to fall to its full down position, closing back contact 20 and causing operation of signal S when the eastbound train entered section IT and this operation of the signal would be continued while this train receded from the intersection through section IT. In the event magnet WXR is the first to be deenergized subsequent to a loss of power, and the armature of magnet EXR is locked at the intermediate position, magnet EXR is reenergized over its second or stick circuit including back contact I4 of relay POR, back contact I5 of magnet WXR. and flagman contact I6 of magnet EXR, with the result the armature of magnet EXR. is picked up off the interlocking mechanism of the relay. If now a westbound train approaches the intersection, and while it occupies the section IT the alternating current is restored. the restoration of power reenergizes relay PCB and track relay 2TB so that magnet WXR is reenergized. With relay PCB and magnet WXR, picked up, magnet EXR. is deenergized and its armature releases to its full down position to bring about the warning operation of the signal S. Interlocking relay IR being now positioned to correspond to normal operation for westbound traffic, the apparatus functions in the usual manner as this westbound train proceeds over the intersection and recedes through the section 2T. If the second or stick circuit for magnet EXR is not provided and the magnet is controlled by the track relay alone, then its armature would have been locked in the intermediate position subsequent to the loss of power, with the result that if power is restored while the westbound train occupies the approach section IT, no warning operation of signal S would be efiected.

It is to be seen, therefore, that I have provided novel and improved control apparatus for highway crossing signals wherewith a. failure of operation of the signal due to a loss of power to alternating current track circuits is avoided.

Although I have herein shown and described but one form of apparatus for control of highway crossing signals embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a highway crossing signal located at an intersection of a highway and a railway track, two track sections formed in said track to extend in opposite directions from the intersection, a track circuit including a track relay and a track transformer for each of said sections, a source of alternating current connected to said track transformers to supply power to the track circuits, a power-off relay'connected to said source and normally energized thereby, an interlocking relay having two magnets one associated with each track section and each magnet provided with a fiagman contact, a pick-up circuit for each magnet and each pick-up circuit including a front contact of the track relay of the section associated with the respective magnet, a stick circuit for each magnet and each stick circuit including a back contact of the power-off relay and the flagman contact of the respective magnet, and circuit means controlled by said interlocking relay to operate said signal.

2. In combination with a highway crossing signal located at an intersection of a highway and a railway track, two track sections formed in said track to extend in opposite directions from the intersection, a track circuit including a track relay and a track transformer for each of said sections, a source of alternating current connected to said track transformers to supply power to the track circuits, a power-off relay connected to said source and normally energized thereby, an interlocking relay having two magnets each of which is provided with a flagman contact, a first enerizing circuit for each of said magnets, the first circuit for a first one of the magnets including a front contact of said poweroif relay and a front contact of a first one of said track relays and the first circuit for a second one of the magnets including a front contact of said power-off relay and a front contact of a second one of said track relays, a second energizing circuit for each of said magnets, the second circuit for said first one of the magnets including a back contact of the power-01f relay and its own fiagman contact and the second circuit for said second one of the magnets including a back contact of the power-off relay and its own fiagman contact, and circuit means controlled by said interlocking relay to operate said signal.

3. In combination with a highway crossing signal located at an intersection of a h ghway and a railway track, two track sections formed in said track to extend in opposite directions from the intersection, a track circuit including a track relay and a track transformer for each of said sections, a source of alternating current connected to said track transformers to supply power to the track circuits, a power-off relay connected to said source and normally energized thereby, an interlocking relay having two magnets one associated with each track section and each magnet provided with a flagman contact, a first energizing circuit for each of said magnets and each of said first circuits including a front contact of the power-off relay and a front contact of the track relay of the section associated with the respective magnet; a second energizin circuit for each of said magnets and each of said second circuits including a back contact of the power-efi elay the .flesmen contact oi the resnee vemoenet. a back e i tact oi the oth a net; and eiremt means including c ntacts f t e interlocking: re ay t operate sa d, s na 4. In combination with a highway crossing signal located at an intersection Of a highway and a railway track, two track sections formed in said track to exte d in opposite directions from the intersection, a track circuit including a track relay and a track transformer for each of said sections, 2. source of alternating current connected to said track transformers to supply power to the track circuits, at power-oil relay connected to said source and normally energized thereby, an interlocking relay having two magnets one associated with each track section and each magnet emcee provided, wit a daemon contact. an auxiliary source of power a first energizin ircuit for each of said 'magnets and each said first circuits including said auxiliary power source in series with a front contact of the .powenoff relay and a front contact oi the track relay of the section asso-. ciated with the respective magnet; a. second en.- ergizing circuit for each of said magnets and each of said second circuits including said auxiliary power source in series with a back contact of the power-ofi relay, the fiagman contact of the respective magnet and a back contact of the other magnet; and .circuitmeans including con.- tacts of said interlocking relay to operate said signal.

EASTON E. PARRILL. 

